Calculator
Every default below is a typical estimate – edit to match your case. Results update instantly as you type.
How it works: formulas and assumptions
The calculator is a link budget: it starts with the power your router radiates, subtracts every loss between the router and a phone or laptop, and checks whether what is left is above the level at which Wi-Fi stays usable. All formulas below are exactly what the page runs.
1. Free-space path loss
FSPL(dB) = 20·log10(d metres) + 20·log10(f MHz) − 27.55Distances below 1 m are treated as 1 m. Centre frequencies used: 2.4 GHz = 2437 MHz, 5 GHz = 5500 MHz, 6 GHz = 6200 MHz. Doubling the distance costs 6 dB; moving from 2.4 to 5 GHz costs about 7 dB more at the same distance, and 6 GHz about 8 dB.
2. Received signal
RSSI(dBm) = EIRP − FSPL − (walls × wall_dB) − (floors crossed × floor_dB)EIRP is the effective radiated power of router plus antennas. Assumed values by power class (2.4 / 5 / 6 GHz): Low 17 / 20 / 18 dBm, Mid 20 / 23 / 21 dBm, High 23 / 27 / 24 dBm. The client is assumed to have a 0 dBi antenna.
3. Wall and floor attenuation (dB, 2.4 / 5 / 6 GHz)
| Material | Per wall | Per floor |
|---|---|---|
| Drywall / wood frame | 3 / 4 / 5 | 10 / 14 / 16 |
| Brick | 6 / 9 / 11 | 14 / 19 / 22 |
| Concrete / reinforced | 10 / 15 / 18 | 17 / 23 / 27 |
| Metal studs / steel deck | 7 / 10 / 12 | 16 / 22 / 26 |
| Glass-heavy (coated) | 3 / 5 / 7 | 15 / 20 / 23 |
These are rounded, typical figures from public propagation literature and are applied to every interior wall you enter. Real walls vary a lot: a bathroom with a mirror and plumbing can cost 10 dB more than a bedroom wall.
4. Geometry
floor area = total area / floors far-room distance = max(2, 0.9 · sqrt(floor area)) m floors crossed (single router) = floor(floors / 2) slant distance = sqrt(far-room distance² + (3 m · floors crossed)²)The router is assumed to sit on a middle floor, off-centre, with the farthest room near the opposite corner. Each storey is 3 m tall. The plan is drawn as a 3:2 rectangle.
5. Usable radius
Usable means a received level of at least −70 dBm. The radius is the largest distance d where EIRP − FSPL(d) − (walls per metre · d · wall_dB) ≥ −70, solved by bisection on the same floor. Walls per metre is your wall count divided by the far-room distance, so a house with many partitions loses signal faster per metre.
6. Mesh nodes
Per floor, nodes = ceil(floor area / (0.65 · π · r²)); the 0.65 factor accounts for overlap needed for roaming and backhaul. If the radius after crossing one floor is at least 0.35 · sqrt(floor area), one node can serve two floors; otherwise every floor gets its own. The calculator then tests combinations of floor groups and nodes per floor, shrinking the far-room distance by sqrt(nodes per floor) and the wall count by the same factor, and picks the smallest total whose far-room signal is at least −70 dBm. An outdoor node is added if the yard point (half a node cell plus the yard depth, with the exterior wall and half the interior walls) falls below −70 dBm.
7. Signal rating
Excellent ≥ −50 dBm, Good −50 to −60, Fair −60 to −70, Poor below −70.
8. Bandwidth model
| Activity | Down (Mbps each) | Up (Mbps each) |
|---|---|---|
| 4K stream | 25 | 0.5 |
| HD stream | 8 | 0.3 |
| Video call | 4 | 3.5 |
| Online / cloud gaming | 15 | 5 |
| Big download / backup | 50 | 10 |
| Smart-home device | 0.5 | 0.3 |
| Work-from-home user | 15 | 10 |
Smart-home devices are treated as always on, so concurrency is not applied to them. Plan tiers considered: 50, 100, 200, 300, 500, 1000, 2000 and 5000 Mbps; the smallest tier at or above the requirement is shown.
9. Wi-Fi standard
Devices = all streams, calls, games, downloads and smart devices plus 2 per remote worker. Wi-Fi 7 if the requirement exceeds 1000 Mbps; Wi-Fi 6E if it exceeds 500 Mbps, devices exceed 60, you plan on 6 GHz, or three or more nodes are needed; Wi-Fi 6 if it exceeds 150 Mbps or devices exceed 20; otherwise Wi-Fi 5 is enough.
A 1,800 sq ft (167 m²) two-storey wood-frame home, 3 interior walls to the farthest room, a mid-power router, defaults for usage.
- Floor area 83.6 m²; far-room distance 0.9 · sqrt(83.6) = 8.2 m; one floor crossed; slant distance 8.8 m.
- At 5 GHz: FSPL(8.8 m) = 18.9 + 74.8 − 27.55 = 66.2 dB. Walls 3 × 4 = 12 dB, floor 14 dB. RSSI = 23 − 66.2 − 12 − 14 = about −69 dBm: Fair, right at the edge.
- The same room at 2.4 GHz comes out near −58 dBm (Good); at 6 GHz near −77 dBm (Poor).
- A single router radius on one floor is about 21 m at 2.4 GHz, 15 m at 5 GHz and 12 m at 6 GHz.
- Bandwidth: active load 144 Mbps × 70% = 100.8, plus 12.5 for smart devices = 113.3, with 25% headroom = about 142 Mbps down, so the 200 Mbps tier. Upload comes to about 47 Mbps.
Conclusion: one router just covers this house at 5 GHz, but a second unit makes the far rooms comfortably Good. That is the kind of borderline case the calculator is built to flag.
Guide: choosing a router, mesh system and plan
Placement beats power
The single most effective fix for weak Wi-Fi costs nothing: move the router. Put it central, high (shelf or wall mount, not the floor), in the open, away from the kitchen, mirrors, aquariums and metal cabinets. Every wall you remove from the path to the farthest room is worth 3 to 15 dB, far more than the 3 dB you gain by doubling transmit power. Most ISP installers place the box where the cable enters the house, which is rarely the best spot for coverage.
Choosing a band
- 2.4 GHz goes farthest and penetrates walls best, but it has only three clean channels, is shared with microwaves and Bluetooth, and realistically delivers 50 to 150 Mbps. Ideal for smart plugs, sensors and the far bedroom.
- 5 GHz is the workhorse: far more capacity, shorter range. Good for streaming, calls and gaming within two or three walls.
- 6 GHz (Wi-Fi 6E and 7) has the cleanest spectrum and the lowest latency, but it is the most easily blocked. Treat it as a same-room or next-room band, particularly with brick, concrete or metal framing.
When to go mesh
If the calculator shows one unit and a far-room signal of Good or better, a single quality router is simpler, faster and cheaper. Once the far room drops below about −67 dBm or the home spans more than two floors, add nodes. A wired Ethernet link between nodes (wired backhaul) gives the best result because the nodes do not spend airtime talking to each other. Without wiring, choose a tri-band system with a dedicated backhaul radio and keep nodes no more than one or two walls apart.
Matching the standard to your household
Wi-Fi 5 is fine for a small flat with few devices. Wi-Fi 6 adds efficiency with many simultaneous devices and is the sensible minimum for a purchase today. Wi-Fi 6E adds the 6 GHz band, which matters in dense apartment buildings where 5 GHz is crowded. Wi-Fi 7 is worth it mainly for gigabit-plus plans and compatible laptops and phones; older devices do not gain speed from a newer router, although they often benefit from better scheduling.
Sizing the internet plan
Download speed is rarely the bottleneck for a household of two; upload and latency are. Remote workers who join video meetings and sync large files need upload most. Cable plans are often asymmetric, with upload around a tenth of download, so check the upload figure before you pay for a higher tier. Fibre plans are usually symmetric. Plan tiers on this page are generic speed grades, not prices; check what your own providers actually offer.
Common mistakes
- Buying on the headline number (such as AX6000 or BE19000). That figure adds every band’s theoretical maximum and says nothing about range or real throughput.
- Placing mesh nodes at the far edge of coverage. Put a node where the main router still gives at least −60 to −65 dBm, so it has a strong link to relay.
- Ignoring the device side. A phone with one antenna will link at a lower speed than a laptop with two, and the router cannot fix that.
- Stacking extenders. Each wireless repeater hop can halve throughput. Prefer one proper mesh system or a wired access point.
- Leaving everything on one SSID name per band without testing. If a device clings to 2.4 GHz near the router, a band-steering setting or separate names may help.
- Forgetting firmware updates and a strong admin password, which matter for security as much as for speed.
Reading the results sensibly
Treat the radius as a planning figure with an error of roughly plus or minus 30 percent. Use it to decide between one unit and two, then walk around with a free signal meter on a phone to confirm. If your measured far-room figure is 5 to 10 dB below the estimate, raise the wall count by one or two and recalculate.
Glossary
- dBm
- Power relative to 1 milliwatt on a log scale. −50 is strong, −70 is the edge of usable, −85 is unreliable.
- EIRP
- Effective isotropic radiated power: transmitter power plus antenna gain, limited by regulators.
- FSPL
- Free-space path loss: signal spreading with distance and frequency in open air.
- Mesh
- Several units sharing one network name and handing devices between them as you move.
- Backhaul
- The link between mesh nodes and the main router, wired or wireless.
- Concurrency
- The share of your devices and activities that run at the same moment.
- Headroom
- Extra capacity kept for growth, protocol overhead and bursts.
- MU-MIMO / OFDMA
- Techniques that let a router serve several devices more efficiently at once, central to Wi-Fi 6 and later.
Frequently asked questions
How far does a Wi-Fi router really reach indoors?
Typically 10 to 20 m (30 to 65 ft) on 5 GHz through two or three interior walls, and 15 to 25 m on 2.4 GHz. In open air the range is far longer, but every wall removes 3 to 15 dB. The calculator shows the radius for each band using your own wall count and material.
What dBm signal do I need for good Wi-Fi?
Stronger than -60 dBm is good for streaming and calls, -50 dBm or better is excellent, -60 to -70 dBm is fair and works for browsing, and weaker than -70 dBm becomes unreliable. Speeds drop and latency rises as the signal falls toward -80 dBm.
Do I need a mesh system or will one router do?
One router is enough when the far-room signal is Good (about -60 dBm) or better, usually in a flat or a home under roughly 150 m2 (1,600 sq ft) on one or two floors with few dense walls. Add mesh nodes when the far room is below -67 dBm, the home has three or more floors, or you need outdoor coverage.
Why is 6 GHz range so short?
Higher frequencies lose more energy over the same distance and are absorbed more by walls and floors. 6 GHz loses about 8 dB more than 2.4 GHz at the same distance, plus a few extra dB per wall. In return it offers wide, uncongested channels and low latency in the same room or the next one.
How many Mbps do I actually need?
Add up what runs at the same time: about 25 Mbps per 4K stream, 8 per HD stream, 4 per video call, 15 for gaming, plus downloads and work. Most homes of two to four people land between 100 and 300 Mbps. The calculator adds your concurrency and headroom, then rounds to a plan tier.
Does my internet plan speed equal my Wi-Fi speed?
No. Wi-Fi sits between your devices and the modem. Your Wi-Fi speed is limited by the lower of the plan speed and what the wireless link can carry at your location, which depends on signal, device antennas, channel width and interference. Good coverage is what lets you use the speed you pay for.
Should I buy Wi-Fi 6, 6E or Wi-Fi 7?
If most of your devices are older, Wi-Fi 6 is plenty. Choose 6E or 7 if you live in a dense building where 5 GHz is crowded, have many 6 GHz capable devices, or have a gigabit-plus plan. A newer router never makes an older device faster, but it can serve many devices more efficiently.
Is wired backhaul really better for mesh?
Yes. A wired Ethernet link lets every node use its radios only for clients, which can double or triple real throughput compared with wireless backhaul. If you cannot run cable, powerline or MoCA adapters are options, and a tri-band mesh with a dedicated backhaul radio is the next best choice.
How accurate is this calculator?
Treat it as a planning estimate with an error of roughly plus or minus 30 percent in radius. It ignores furniture, appliances, interference and the exact layout. The formulas and assumptions are published in the how-it-works section, and a phone signal meter test in the far room is the best final check.
About
We are an independent publisher of free buying-decision tools. This calculator exists to turn a vague question, “will this router cover my house and my family?”, into numbers you can check.
Mission. Help people avoid paying for the wrong router, too many mesh nodes or an internet tier they do not need.
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Editorial approach. Formulas and assumptions are published in full above so you can verify and challenge them. When we learn of an error we correct it and update the revision date. Corrections are welcome through the contact section.
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Disclaimer
Results are estimates only and are not professional network engineering or purchasing advice. Real Wi-Fi performance depends on wall construction, furniture, interference from neighbours, router firmware, device antennas and your internet provider. The outputs depend entirely on the values you enter and on simplified assumptions published above. We do not guarantee any coverage, speed or saving. Router and plan recommendations are generic categories, not endorsements of any brand, product or provider, and tier names are not offers or prices.